It is not rare to see one species take to another, especially during whelping, because giving birth is the best time for adaptive nursing, Stoenner said.

Although Buffy and Marty are compatible now, Marty is not out of the woods yet.

It will be a few more weeks before Marty�s eyes open, and if he makes it, he most likely will not be able to be released into the wild, Stoenner said. But the vet thinks that if anybody can ensure that Marty survives, Wills is the one.

"She�s a hard-core gal," Stoenner said. "She doesn�t give up."

The Chihuahua-chipmunk relationship has been among the most unusual in Stoenner�s 12-year career.

"It�s kind of neat," he said. "You like to think there�s good going on, and this supports that."

Buffy, who will be 4 next month, gave birth to one surviving female puppy Thursday.

But Wills, who has other Chihuahuas, thinks one chipmunk will be enough.